Fuels that are gaseous at standard ambient temperature and pressure (“gas fuels”) may comprise, for example, methane, ethane, propane, butane, pentane, and mixtures of two or more of these hydrocarbons. Standard ambient temperature and pressure is 25 deg. C and 101 kPa. Gas fuels may also comprise small amounts of other gases including propylene, butylenes, and additives including, for example, odorant gasses in the form of ethanethiol, tetrahydrothiophene, or amyl mercaptan for the detection of gas leaks.
Gas fuels may be compressed to form a liquefied gas fuel. For example, butane, propane, and fuels containing mixtures of these hydrocarbons may be sold as liquid petroleum gas or liquid propane gas, either of which may be abbreviated to LPG. A liquefied gas fuel may be stored in a pressure vessel, examples of which include but are not limited to cylinders and tanks including LPG bulk storage tanks (“LPG bullet tanks”), and liquefied natural gas storage tanks.
Within the pressure vessel is an interface between the liquefied gas fuel and the vapour thereof. The vapour is located above the liquefied gas fuel and within an upper part of the pressure vessel. A vapour outlet in the form of a vapour outlet valve assembly may be attached to the upper part of the pressure vessel.
The quantity of liquefied gas fuel within a pressure vessel may be determined using a liquid-level gauge in the form of a float level-gauge, an example of which is shown in FIG. 1 and generally indicated by the numeral 10. The float level-gauge of FIG. 1 is a ROCHESTER brand float-level gauge which is used with LPG bulk storage tanks, however other examples include TAYLOR and COTRAKO brand float gauges. The float level-gauge comprises a float 12 connected to a stem 14 via a movable joint 16, and a head 18 from which the stem 14 depends. The head 18 is shown in further detail in a top perspective view thereof in FIG. 2. The float level-gauge 10 penetrates a pressure vessel wall and the head 18 is externally attached thereto with fasteners in the form of bolts that pass through bolt passageways 20 to a flange or other suitable mount that is integrated with the pressure vessel, for example by welds or screws. A seal that surrounds the penetrating stem 14 may be sandwiched between the head 18 and a flange integrated with the pressure vessel wall.
The float 12 follows the interface between the liquefied gas fuel and the vapour thereof. A magnet located at the head 18 is operationally coupled to the float 12. Movement of the float 12 is transmitted to the magnet via a gear system at the joint 16. Vertical movement of the float 12 is transformed to a rotation of the magnet at the head 18, and consequently a rotation of the magnet's magnetic field. The magnet is mounted to rotate around the stem axis. Generally, the magnetic field may be followed by a user visible external needle, the orientation of which may indicate the height of the float and the interface that the float follows. The use of the magnet enables measurement of the quantity of liquefied gas fuel within the pressure vessel while maintaining a high strength seal, enhancing safety.
While the description above specifically mentions liquefied gas fuel, the description may generally apply for any suitable type of liquid within a vessel that may or may not be pressurised, for example liquefied ammonia, cryogenic liquids including liquefied natural gas and liquefied permanent gases, and refined petroleum products including petrol, kerosene, and fuel oil.
The pressure within a vessel may be measured with a pressure gauge. The pressure within a vessel containing a non-liquefied permeant gas in its gaseous state, for example, may be read to determine the quantity of gas remaining in vessel.
When a user observes that a gauge indicates that the contents of a vessel is low, the user may contact a supply company to refill the vessel.
Natural gas is generally delivered to a premises via a service line connected to the gas mains. A gas meter may be inserted in the service line to determine the quantity of gas that has been consumed at the premises for billing and other purposes.
Premises may have a plurality of LPG cylinders onsite. An LPG gas changeover valve may control which of the plurality of gas cylinders is connected to a gas outlet. A person may order a gas delivery when a bottle is depleted and the LPG case changeover valve switches to another cylinder.
Electronic devices may interface with gauges, gas meters, an automatic changeover valves for example. There may be a need to do at least one of the following:                activating and deactivating an electronic device        determine whether an electronic device is oriented correctly        determine whether an electronic device and/or vessel or valve attached thereto has been tampered with        track the position of a vessel.        